In the handling of sheet material such as is used for building construction, it has been common in recent times to provide a portable sheet bending brake wherein sheet material is clamped between an anvil member and a clamping surface and a bending member is hinged for bending the sheet material about the anvil member. Typical sheet bending brakes are disclosed in U.S. Pat. Nos. 3,161,223, 3,481,174, 3,482,427, 3,559,444, 3,187,075 and 4,240,279.
As shown, for example, in the aforementioned U.S. Pat. Nos. 3,161,223, 3,559,444, 3,817,075 and 4,240,279, the anvil member is clamped into position by means of a backing plate that has inclined cams underlying a portion of the fixed frame so that when the plate is moved longitudinally by a hand lever, the cams are moved into and out of position clamping and unclamping the backing plate.
In the aforementioned U.S. Pat. Nos. 3,481,174 and 3,482,427, the anvil is supported by pivoted bars that, in turn, are connected by links to a handle that is pivoted on the frame of the brake so that rotation of the handle moves the bars and, in turn, the anvil into and out of clamping position.
It has also heretofore been suggested that eccentric cams be utilized for moving the anvil member into and out of position as shown, for example, in U.S. Pat. Nos. 3,383,899, 4,092,841 and 4,081,986.
In the aforementioned U.S. Pat. Nos. 3,481,174 and 3,482,427, a floating compensator has been pivoted on the bending member such that the compensator engages an area of the workpiece and remains in engagement with the same area so that the workpiece is not marred or scuffed during the bending. Such an arrangement has proved very effective in portable sheet bending brakes. However, as the bending member approaches and exceeds a position for making a bend of 90.degree. or greater, the area of application of force on the workpiece shifts radially inwardly so that the bending arm or lever is less and a greater force is required to move the bending member. In addition, there may be a tendency for the force to be concentrated on less than the total area of the compensator.
Among the objectives of the present invention an to provide a portable sheet metal bending brake which includes an improved floating compensator which remains in contact with a greater area than the compensator of U.S. Pat. Nos. 3,481,174 and 3,482,427; which requires a lesser force to move the bending member, especially when the workpiece is bent to greater angles; and which permits a second and tighter bend to be performed without clamping the workpiece.
In accordance with the invention, the hinged bending member is provided with a floating compensator that comprises a compensator member pivoted to the bending member and a workpiece engaging pad pivot to the compensator member. As the bending member is swung to bend a workpiece, the pad engages the surface of the workpiece and remains in contact with the workpiece at the same area by the relative pivotal action of the bending member, the compensator member and the pad.